This invention relates to a torsion damping device which is mounted between two coaxial rotating members for transmitting a rotational torque between the two said members, with damping out of vibrations and torque oscillations, and it is applicable in particular to friction clutches for motor vehicles.
Conventionally, a torsion damper includes two guide rings which are coaxial with the two rotating members and which are coupled for rotation with each other and with one of the rotating members, an annular damper plate disposed between the two guide rings, and means for coupling the said annular damper plate in rotation to the other rotating member. Circumferentially acting resilient members, such as helical springs, are mounted between corresponding windows of the damper plate and the guide rings, and are in engagement at their ends on the radial edges of the said windows so as to transmit a rotational torque between the guide rings and the annular damper plate, while absorbing vibrations and torque oscillations by elastic deformation.
The axes of the said springs a-re in the plane of the annular damper plate, in such a way that, during angular displacement between the guide rings and annular damper plate, one end of each spring is in axial abutment on a radial edge of a window in the annular damper plate, while its other end is in abutment on the radial edges of the windows in the guide rings, substantially symmetrically with respect to the plane of the annular damper plate, with the resultant of the forces applied at the said other end of a spring being axial with respect to the spring. In such a torsion damper, the springs work in axial compression, which is beneficial to the length of their useful life.
In order to reduce the number of components and the axial size, and also the cost, of such a torsion damper, it has previously been proposed to replace the known structure having two guide rings and an annular damper plate with a simpler structure which only has two rings, one of which is coupled in rotation to one rotating member, the above mentioned springs being disposed between these two rings in housings which are defined by windows or cavities in the said rings. During an angular displacement between the two rings, each spring is in abutment at one end on a radial edge of a window of one ring, and at its other end on a radial edge of a window of the other ring, but these abutments are offset with respect to the axis of the spring, so that the compression forces from the springs are no longer axial but are oriented diagonally, and the compression of the springs is accompanied by bending which tends to displace them with respect to the axis. In order to avoid such displacement, it is necessary to provide means for guiding the springs, which give rise to friction effects liable to disturb the operation of the torsion damper. It is also necessary to over-dimension the springs so that they support the additional stresses caused by their being compressed diagonally.
A main object of the present invention is to overcome these drawbacks in the known art, but without in so doing increasing the number of components, nor the axial size or cost of a torsion damper of the type described above.
To this end, it proposes a torsion damping device, mounted between two coaxial rotating members for transmitting a rotary torque from one member to the other with damping of vibrations and torque oscillations, comprising:
two rings coaxial with the two rotating members,
rotational coupling means between the two rotating members and the rings,
circumferentially acting resilient members mounted between the rings in housings which are formed in the said rings and which include means for abutment of the ends of the resilient members,
characterised in that the two rings are rotatable with respect to each other and with respect to the two rotating members with a limited angular displacement, and are urged in rotation by the said resilient members in opposite directions tending to put them into abutment on the means for coupling them to the respective ones of the rotating members.
In the device according to the invention, and by contrast with what is found in the known art, each ring is rotatable with respect to the two rotating members and with respect to the other ring, independently of that other ring. This then enables a first ring to be associated with a first rotating member and the second ring with the second rotating member in one direction of rotation, and conversely, the first ring with the second rotating member and the second ring with the first rotating member in the other direction of rotation, so that it enables the two directions of rotation to be distinguished from each other.
Each ring acts in only one direction on the resilient members, and each resilient member is in constant engagement at one end on an element of one ring, and at its other end on an element of the other ring. This results in improved engagement and improved holding of the resilient members, together with a reduction in wear of the latter and an increase in their useful life.
In addition, because of the constant engagement of the resilient members at each of their ends, it is of advantage to make use of elastomeric blocks as resilient members, in place of the traditional helical springs.
Fitting of the device according to the invention is also more simple than in the known art, because none of the rings has to be coupled in rotation with a rotating member, and this avoids operations of seaming or the like which are used in the known art. Consequently, renovation and maintenance of the clutch are also simplified.
The two rings are preferably identical. According to another feature of the invention, each ring is in engagement on the means for coupling the said ring to one of the rotating members, and a circumferential clearance exists between the said ring and the means for coupling it to the other rotating member.
This, in particular, reduces shocks and damage to the rings and/or their coupling means, in operation.
In a first embodiment of the invention, the two rings are made by press-forming or moulding with the housings of the above mentioned resilient members, each housing having at one of its ends an axial engagement face for an elastic member placed in the said housing.
The opposite end of the housing does not have any axial engagement means for the resilient member.
Preferably, the housings are defined in the said rings by recesses which are situated face to face as between one ring and the other, each recess being joined at one end to a boss which projects towards the other ring so as to define the axial engagement face of a said resilient member.
In a further embodiment of the invention, the said rings are flat and the housings of the resilient members are defined by windows in the rings, with each window having a radial side which serves as an axial abutment for a resilient member and which includes means for centring and retaining that member.
These two rings are simple and inexpensive to make, and can be mounted in engagement on each other.
According to a further feature of the invention, each ring includes a set of teeth meshing, with a predetermined circumferential clearance, with a set of teeth of one of the said rotating members.
The set of teeth of the rings are formed on their inner periphery, and the set of teeth of the said rotating member is formed, for example, on the outer periphery of a cylindrical surface of the said rotating member.
When the rings urged into rotation by the said resilient members in opposite directions are in abutment on the said rotating member, the teeth of one ring are in engagement on the flanks of the teeth of the rotating member and the teeth of the other ring are in engagement on the opposed flanks of the teeth of the said rotating member.
The means for coupling the rings in rotation to the other one of the rotating members comprise, for example, fingers fixed to the said rotating member and engaged in circumferential slots of the said rings, the slots being of limited angular extent.
Preferably, at least one slot of one ring is positioned with respect to a slot of the other ring in such a way that the same finger fixed to the said rotating member passes through the two said slots.
In another version, the means connecting the said rings to one of the rotating members comprise lugs fixed to the rings and engaged between abutments carried by the rotating member, the said lugs being substantially radial.
According to yet another feature of the invention, the torsion damping device constitutes a unitary assembly, the two rings being in hooked engagement on each other by means of circumferential lugs offset axially so as to engage within each other and to oppose axial separation of the rings.
The said unitary assembly can thus be pre-assembled and then fitted on the rotating members.
The device according to the invention can be used for absorption and damping of vibrations and torque oscillations between two rotating members of any type whatsoever.
It can also be used as a main damper and/or as a predamper in a torsion damper of a friction clutch for a motor vehicle.
Where it constitutes a predamper mounted in series with a main damper in a clutch, it can be mounted either inside the main damper or on the outside of the latter, with a very much reduced axial size.
The invention will be better understood, and further features, details and advantages of it will appear more clearly on a reading of the following description, which is given by way of example and with reference to the attached drawings, in which: